Centrifugal clutch



Dec. 19, 1950 c. M. EASON CENTRIFUGAL CLUTCH 5 Sheets-Sheet 4 FiledMarch 5, 1947 llll 1N VEN TOR.

a 0 w FL M w 7v 7 w w i at enteci Dec. 19, l95

CENTRIFUGAL, [CLUTCH Clarence M. Eason, Waukesha, Wis., assignor toIndustrial Clutch Corporation, Waukesha, Wis., a corporation ofWisconsin Application March 5, 1947, Serial No. 732,414

9 Claims. w l The present invention relates to centrifugal clutcheswherein centrifugal force is utilized to automatically controlengagement of driving and driven clutch members.

One of the principal objects of the invention is to provide an improvedcentrifugal clutch which is capable of transmitting a large startingtorque to the load without objectionable overheating or wear of theclutch. More specifically in this regard, the present clutch hasparticular application to power driving situations where the load to bedriven has a relatively high starting torque, typically represented byair compressors and the like.

Another more particular object of the invention is to provide animproved centrifugal clutch in which there is a very substantialdifferential between the rotative speed at which clutch engagementoccurs and the rotative speed at which clutch release occurs. Forexample, in the preferred embodiment of my invention actual clutchengagement will not start until the rotative speed of the drivingelement has been brought up to a clutching speed which closelyapproaches the normal running speed of the device, and, conversely,actual clutch release will not start until the rotative speed has comedown to a releasing speed which is approximately half that of clutchingspeed, or even less. Thus, assuming a gasoline engine or other likeprime mover arranged to drive an air compressor at approximately 1800revolutions per minute, my improved centrifugal clutch will not initiateactual clutching engagement until the engine speed is up in theneighborhood of 1200 R. P. M., whereupon the clutch will automaticallyengage and will maintain driving engagement until the rotative speed ofthe unit has come down to approximately 500 R. P. M. to 600 R. P. M., oreven less. This enables a large amount of kinetic energy to be stored upin the prime mover, as for example in the fly-wheel of a gasolineengine, before clutching engagement is even started. Hence, a loadhaving a high starting torque can be successfully driven by my improvedautomatic centrifugal clutch. If the high starting torque of the loadshould momentarily bring the speed of the prime mover down considerablybelow the clutching speed at which clutch is being purposely reduced forreleasing the clutch.

Another object of the invention is to provide an improved centrifugalclutch in which the act of automatically engaging the clutch and the actof automatically releasing the clutch are both relatively rapidoperations so that there is no considerable interval of slipping orpart-way engagement, which is very likely to overheat or burn up aheavily loaded clutch.

Another object of the invention is to provide improved centrifugalmechanism utilizing pivoted centrifugal weights acting in opposition toresisting or retracting springs, wherein an inverse relationship existsbetween centrifugal weight action and retracting spring action. That isto say, when the effectiveness of the pivoted centrifugal weightsincreases with rising speed and change of pivotal position of theweights, then the effectiveness of the retracting springs decreases;and, conversely, when the effectiveness of the pivoted centrifugalweights decreases with falling speed and change of pivotal position,then the effectiveness of the retracting springs increases. In thepreferred embodiment of the invention, this is accomplished by havingeach pivoted centrifugal weight transmit its clutch engaging forcethrough a variable radius arm which increases in effective length as thepivoted weight swings outwardly in response to increasing centrifugalforce, and which radius arm decreases in effective length as the pivotedweight swings inwardly in response to spring retraction. As the inversecounterpart of this, the retracting spring acts through a variableradius arm which decreases in effective length as the pivoted weightswings outwardly under centrifugal force, and which increases ineffective length as the pivoted weight swings inwardly in response tothis spring retraction.

Another object of the invention is to provide an improved centrifugalclutch in which the centrifugal forces set up in the major parts of theclutch act cumulatively for producing clutch engagement. For example,the driving clutch elements consist of pivoted clutch shoes in whichcentrifugal force tends to produce clutch engagement, thereby augmentingthe action of the pivoted cen trifugal weights, with the result thatthese weights need not be as large as they would have to be if thedriving clutch elements did not have a cen trifugal engaging action.

Another object of the invention is to provide an improved constructionof centrifugal clutch embodying a simplified and readily actuatable formof adjusting mechanism for adjusting the clutch to compensate for wearof the friction surfaces or other wear of the parts.

Another object of the invention is to provide a shoe type of clutch inwhich the clutch shoes have a free floating mounting on the drivingmember of the clutch. This free floating mounting enables the clutchshoes to automatically center themselves with respect -to the drivenclutch surface as they are forced into clutching engagement with saiddriven clutch surface.'

This free floating mounting enables the automatic centering to occurwith respect to'angular misalignment, or offset misalignment,.or both:

Thus, if there is angular misalignment, or offset" misalignment, orboth, between the driving and driven members of the clutch, the freefloating mounting enables the clutch shoes to center themselvesaccurately within the driven clutc'h element, and to rotate inexactconcentricity with this driven clutchelement,*even though they arereceiving their entire torque load or drivingLforce from-a drivingclutch member which isiout :of alignment with respect to the orbit inwhich the clutch shoes are now rotating. One of themore specificobjectsvvof :this free floatingjmounting is to'provide a construction inwhich the torqueois transmitted from the. driving member of the clutchto the driving shoes through a floating torque transmitting connect-ion.Another more specific object of thefree floating mounting is to providea construction in which1the reaction pres-' sure of the clutchingengagement is transmitted from shoe to shoe, instead of to a spider:or-other supporting structure The shoe assembly then virtual-1y becomesa self -contained independent unit/.

Another object' of the invention is to provide an automatic centrifugalclutch having'thefeatures first de'scribed,-and also characterized bythe free floating mounting last described. this regard," the pivotedcentrifugal weights, the retr'actingsprings, andthe adjusting mechanismall have free 'floating mounti'ng withrespect to thedriving-clutch'member. I Other objects-,features and advantages oftheinvention will appear 1 from v the following detail description-of onepreferred embodiment of the in 'ii'tion: In theaccompanyingdrawings-illustfa'ting suchembodiment j Fi ure l-is an axialor front view oi-one-embodiment of the invention; with-partsbroken away;

Figure 2 is asimilarviewpfthissame embddiment as viewed from theopposite side; Figure '3 is a" transverse-sectional view takenapproximately on the section planes 3' 3 of Figtires '1 and 2, theadjacent centrifugally'responsiv e pivoted Weight being shown-insection;-

Figure 4 is a transverse sectional vie\'2'v -tal-:en' approximately onthe section planes-44 of Figur'e'sfl and 2;

Figure 5 is a detail sectional viewshowing the adjustable mounting 1 ofeach retracting spring and its connection with its respectivecentrifugally responsive weight;

Figure 6 is a detail sectionalview of the adjusting mechanism, takenapproximately on the plane of the'line 86"-of Figure 2;"

Figure '7 isa diagrammaticview of-Eth'eoper ating relationship of thepivoted centrifugal weight and the retracting spring in'the aboveembodiment, showing the angular positions of the centrifugal weight andthe corresponding angular positions of the lever armwhich" connects withthe associated retracting spring; and

Figure 8 is a graph showing the variations of clutch engaging torque oneach clutch actuating eccentric for the different angular positions ofthe pivoted centrifugal Weight at different engine speeds, and alsoshowing the opposing spring pressures exerted by the retracting springin the different angular positions of thepivoted centrifugal weight.

Referring to the preferred embodiment of the invention, illustrated inFigures 1 to 6, inclusive, all of the operating parts of thisembodime'n't are carried by a rotary mounting ring 20 which isadapted tohave bolted attachment to a suitable prime-mover conventionallyindicated at 2|; In the'typical case of an internal combustion enginearranged to drive an air compressor, the prime-mover 2! would be the flywheelof the internal combustion engine, this fly wheel supplying a largeamount of kinetic energy at the time of clutch engagement for starting aload .havingahigh starting torque, such as a conventional aircompressor. The driven member through which the centrifugal clutchtransmits the engine torque to the compressor is preferably in the formof a clutch drum, 22 which is suitably secured to the crankshaft of thecompressor.- The clutching shoes of the centrifugal clutch are adaptedto swing outwardly and establish clutching engagement with the innersurface of this clutch drum 22, as will be later described;

The driving ring 29 comprises an annular bolting flange 25 having holes26 therein .for receiving bolts or.-cap screws 2! which fasten theflange 25=to the fly wheel 2 I. This driving ring 28 is preferably acasting, and at two diametrically opposite points it is formed withlaterally projecting arm portions 28 whichare joined by a diametricallyextending bar portion 29 formed as an'integral part of the arms 28 andbolting flange 25. Spaced outwardly from each arm portion 253 is anotherarm portion 28 formedintegraltherewith and with the cross bar portion29, these two arm portions 28,22 constitut ing thetwosidearms-of a yokedefining a pivot openingfil therebetween; There are twoof theseyoke-formations at diametrically opposite points" ofthe driving ring,and'these yokes afford pivotal support for the pivotallyanchored ends-ofthe arcuate clutch shoes: As shown in Figured,- the"transversebar-portion 29-is formed 'withan apertured boss '33- at its center inwhich is clamped a shouldered'pin 34 held in place by a nut'as screwingover-a threaded end of thepin'.

The other end of said pinis formed with splayed flat surfaces 3'! atdiametrically opposite sides; these surfaces 3'9 functioning as stopsurfaces for limiting the inward swinging movement of the pivotedcentrifugal weights-,- as-will be presently described;

Referring now to thearcuateclutch shoes andtheir mounting'in'theyoke-arms 28;=28-, it will be seen from Figure 2 that there are two ofthese arcuate clutch shoes, designated 38, preferablycomposed ofcastings of duplicate form As shown at the bottom of Figure 3,eaclrclutchshoeis formed with a laterally-projecting outer flange 39 towhich any-suitable clutch facing material 4| is securedby rivets or manyother suitable manner. The exterior curvature of these clutch shoescorresponds substantiallywith the internal radius of the clutch drum'22. The pivo'tally-anchore'd end of eachclutch' shoe is formed with apivot eye 42 which extends into the yoke opening 3| and whichispivotally supported upon a pivot thimble or sleeve 43 extendingthrough pivot openings 44 in the yoke arms 28, 28. Mounted with a snugrotative fit within each bearing thimble-43 is an adjustable bearing pin45 which pivotally supports the link connections extending to theswinging end of each clutch shoe, as I shall presently describe.Attention is now directed to the aforementioned free floating mountingof the clutch shoes and clutch actuating parts on the driving clutchring 20. This free floating mounting is obtained by a yieldable bushingmounting of the bearing sleeve 43 and bearing shafti45 within thebearing openings 44. As shown in-the upper part of Figure 3, thisarrangement comprises pairs of yieldable bushings each consisting of aninner metallic ring 46, an outer metallic ring 41 and an interveningresilient-ring 48 of rubber, neoprene, or other deformable plasticmaterial suitable to this purpose. The intervening resilient rin 48 maybe vulcanized or otherwise secured to the adjacent surfaces of themetallic rings, if desired. This resilient material is preferablyprestressed or precompressed in its introduction between the metallicrings. inner metallic ring 46 has a snug fit over the end of the bearingthimble 43 and the outer metallic ring 41 has a snug fit within thepivot aperture- 44. It will be noted that this free floating mount ingis effective both for the bearing sleeve 43 and also for the bearingshaft 45 within this sleeve. Thus, the yieldable bushing affords a freefloating mounting for the pivotally anchored end of each clutch shoe,and also a free floating mount-- ing for the link connected end of eachclutch shoe, as will hereinafter appear. This free floating mounting ofboth ends of each clutch shoe 38 enables the two clutch shoes to effectaligning adjustments with respect to the axis of the fly wheel 2| andwith respect to the axis of the driven clutch drum 22. That is to say,it enables the two clutch shoes to automatically center themselves withrespect to the inner cylindrical clutching surface of the driven clutch.drum 22, while. stillv receiving the entire driving torque from thedriving clutch ring 28 which may be revolving in a different orbit.Hence, the clutch structure canadapt itself .to a considerable degree ofangular misalignment and also ofiset misalignment between the drivingelement 2| and driven element 22. Also, as will later appear, thereaction pressure of clutching engagement is transmitted directly fromshoe to shoe, and not to the driving ring 20.

Referring now to the manner of link connecting the outwardly swingingends of the two clutch shoes 38, 38 to the two adjustable bearing pins45,,

this comprises an outer link 5| and an inner link 52, this inner linkconstituting one arm of a twoarmed supporting member 52 which carriesthe centrifugal weight and retracting spring, as will be laterdescribed. Each outer link 5| (Figure 2) has a pivot eye 53 at its innerend which engages over a reduced extension 45a projecting outwardly fromthe shaft 45, and each inner link 52 is formed with a pivot eye 54 whichengages over a corre-- sponding extension 451) projecting inwardly fromthe other end of the shaft 45. These oppositely projecting extensions45a and 451) are both formed as eccentric cranks, both aligned with eachother so as to have the same degree of eccentricity with respect to theaxis of the pin 45. Hence, it will be seen that rotation of the shaft 45within the bearing thimble 43 will impart identical degrees of eccentricthrow to the eccentric extensions 45a The and 45b for giving identicaldegrees of inward and outward adjustment to the links 5| and 52. Thiseccentric adjustment transmitted to the brake shoes through the links 5|and 52 is primarily a wear adjustment to take up wear in the outerfriction surfaces of the clutch facings 4|.

Referring now to one form of manual adjusting mechanism forsimultaneously adjusting the eccentrics 45a and 45b for the two clutchshoes,

it will be seen from Figure 3 that a shaft extension 450 projectsoutwardly from the eccentric portion 45a and has a sector gear 56 keyedor splined thereto transmitting rotative movement to the shaft 45.Mounted loosely on the shaft extension 45c inside of the sector gear 56is a ring 51 to which is secured a small stamping or cast-, ing 58 inthe form of a bearin hanger which is formed with two spaced bearings 59,59 (Figure 2). A retainer washer 6| or like retainer member holds thesector gear 56 and ring 5'! from displacement off the outer end of theshaft extension 450. It will be understood that the above describedconstruction is duplicated on the eccentric shaft 45 which mounts theother clutch shoe at the other side of the assembly. Rotatably mountedin the spaced bearing hubs 59 at each side of the assembly is a stubshaft 63. Pinned to these stub shafts between the pairs of bearings 59are adjusting worms 64 and 55, one having a right hand thread and theother a left hand thread, these threads meshing with the teeth of theopposite sector gears 56. The inner ends of the two stub shafts 63 arecoupled together by a coupling stem 66 which is pinned to both shafts.The aligned assembly of stub shafts, adjusting worms and coupling stemis arranged to extend diametrically across the center line of theassembly to engage opposite peripheral sides of their respective sectorgears 56, so that the as-. sembly is statically and dynamicallybalanced. The stub shafts 63 are provided with outer heads 68, and oneor both of these heads is provided with a screw driver slot 69.Adjustment for wear can therefore be easily effected by insertin a screwdriver in the slot 69 and rotating the two adjusting worms 64 and 65 inthe appropriate direction for causing the eccentric shafts 45 to beadjusted for thrusting the links 5i and 52 in an outward direction forcarrying the inwardly movable ends of the clutch shoes 38 into closerproximity to the inner surface of the driven drum 22. Compressionsprings H confined between the outer ends of the coupling stem 66 andthe adjacent bearings 59 function as friction lock washers to hold theadjusting worms 54 and 65 against accidental turning after an adjustmenthas been made. The clutch assembly rotates in a counterclockwisedirection, as viewed in Figure 2, and hence it will be seen that theseinwardly movable ends of the clutch shoes are the leadin ends.

Referring now to the automatic centrifugal mechanism which governs theautomatic engage ing and releasing of the clutch, the outer ends of thepressure links 5| and 52 are formed with pivot eyes 13 and 14 (Figure 3)which have operative connection with the actuatable ends of theirrespective clutch shoes through eccentric shafts 15 which are quitesimilar to the eccentric shafts 45 which mount the anchored ends of theclutch shoes. As shown in the lower portion of Figure 3, each shaft 15is rotatably mounted in the pivot eye 16 of the clutch shoe, withantifriction pin or needle bearings 11 interposed between the shaft !5and the pivot eye it. Eocene tric extensions 15a and 15b project inalignment from-opposite ends-.of the shaftIS-T andi haverotatablamounting; in the pivot .eyes 13' and; .Hrof. the; pressure:links. Anti friction: pin bearings- 18 arezalsoj preferably interposedbetween these'aeccentric extensions and the pivot eyes of the pressure.links. Projecting inwardly from the. in.- ner extension portion lfibqis.a furthershaftaextension'l'5c to which the torqueforces are appliedwhich govern the automatic operation. of. the. clutch. .These forces arecreated by centrifugally: responsive weighted levers 8| which: aremounted on the shaft. extensions c and whichhaveth-eir outward-swingingmovements opposed. by resist;-

ance springs 82. .As shown in Figure 1, these.-

Weighted levers or-arms 8! .are preferably ofiangular iormatiornasviewed from theside, each of thesegleverscomprising a mounting eye 83;at: one end,za ;series of weights 84 at the-.other-end, andanintermediate pin 85 therebetweento which the. tension spring 82isconnected. As shown in -Fig ure. 3;. each. of thesecentrifugalllevers: imaderupofrtwo similar stampings heldin spacedrelationby-interposingyt'he Weights 84. between the outer portions of thestampings, the weightszand lever stampings beingsecured together by thetrans.- verse rivets 86. The mountingeyes83 havepolygonal openingstherein. which engage splayedsurfaces .on the shaft extensions150,.Wh816by these weighted levers are .secured'fast .to the eccentric:shafts 75. Anysuitable retainer ring 88; engages over; the shaftextensionaand prevents outward displacement of the weighted .levertherefrom, The transverse pin 85 which is:provi'ded for: es.- tablishingconnection with :the. tension spring-82 carries axroller or sleeve 89,with an anti-friction pinbearing 9i interposed. between the connectingpin 85 and the sleeve. 89. The tensionsspring 82. hasra hooked-end 82a.which engages in an external groove in the sleeve 89. The opposite .end'

of the. tension spring .is also formed with a hook.

portion 821) which hooks over an adjustable anchor stud 93 carriedat the.outer end of arm 52'. Referring to Figure 5,. this'anchoring stud 93isrof adjustable .eccentricsconstruction.for en- .abling.1the-..tensionof the .spring 82 to be. readily adjusted. Thestud 93'projectseccentricallyirom the hexagon head .96 of. .a threadedshank 9.5 whichextends through. an aperture '36 inarm 5.2 and receives alocknut91:0ver2its-threaded end. 'Byureleasing the .lock nut 5'!thiswthreaded.

shank can'be. rotated. so as. to; shift the-anchor"- ing stud 93 eitherinwardly or outwardly and thereby decreaseor increase the tension. ofthe spring 82.

.The operation .of -the clutch willbe best understood by referringnow to.the largeiscalediagram. of? Figure 7. and the plotted curves 20fFigure-8. When the engine is standing idle,:an'd alsouwhen it, isrunning at relatively low non-clutching speeds. .the tensionv springs8.2 hold, .the. two.- centrifugal levers 8| at the. inner limits oftheir swinging movement, with the. inner edges .of said'. leversabutting against the. stop-..surfaces 321 .of the central stop pin 34.Whenthe engine is set. into operation and has its speed increased uptoward .the automatic clutching point, :it will 'be seen thatcentrifugaliforces acting. in ithezcentrif. ugal, levers: 8| will tendto. swing theselevers out:- wardlyaround the axes of the'actuatingeccenetries 15. Centrifugal forces .are also :acting. atthis time within theclutch shoes 38'themselves,v tending .to swing the clutch shoesoutwardly, but consideration will be confined for thetime being. to thecentrifugal forces acting. in the weighted levers :81. It will beassumed .thatatheicenter ofi gravity orercentrifugalijm.C:-G;:ofieach=weighted lever; falls at a pointribetwe'en.-the rivets86,1and' that this center cof ..;gravity-. 1 of the lever. -mcves.

along the iarc indicated by dotted line as r the weighted; lever:swingsfaroundtheax-isz of; the; ac-

tuatingweccentric. :15; Each weighted: lever has airangessoi: throw ofiapproximately 50- degrees, andflrfhava marked off. on this arc X' thedifferent nos'itionsxofnthis 'centerpof-i gravity i as. -that.ipointmoves; throughq each fivedegrees. of. swinging movement; The position.marked: 45; degrees rep-- resents: the" normal .clutcheengaged running;position. Yet .'-the center of gravity, and the position marked :50fdegreesrepresents a rangefioitover-- travel to;provide for wean of the-clutch:surfaces.

Referring now to the motioni otfithe -springconnecting .pin 8 5, theaxis .of this';pimswingsthrough an arc .dBIlOIbBdxbY- the; dotted lineY. Correspondingly, I have; markednoif. .five: degree: positions on.thiscare?!- -showing --the different-.positions-of the pin axis i-astherenter ofmgravity of.-the: -weig ht+ ed lever movesoutwardly througheach five degrees along the: arc X. It. will; be noted thatas the center.ofzgravityec. ofithe. weightedileyer moves outwardly along; the arc. X,itsxradialdistance-irom-the rotative= axisnof; the-entire clutch:assembly increases,.. whereby: it .1. revolves 111/3110:- cessiveiy.larger: orbits around the clutch; axis. This. means that the.angularvvelocity off the.

weighted lever 1 around-theaclutch axis increases,

and; of course' the. centrifugal-force.in-the weight: edilever also.increases. ItzWill .also/be; notedz-that the center r of gravity C. (G.of j-the" weighted leverhaswayrelatively short length of.. efiective'radius.

arm or: moment arm-around the 'pivot axis of the ilever-"whenthe lever;is in its inwardly r re.- tracted; position, .'.and' that this;effective radius:

armincreases: continucuslyras -the:. center ofrgrav ity. swingsoutwardly-toward andrintogthe 45 de: greeposition. Hence, thecentrifugal. force or the. weighted "lever first-.tendsxto exert:axreiatively. small; torque: xor moment; :arm onnthe actuating.

eccentric -I 5, gand as the :engine speed'zincreases' andtheweighted:levera startsztoiswingwritward ly; :this:.toi:queaonmomentiarmstendslto act with. increasingzefiectiveness:onitheactuating:eccen trio; 1 5.. Rotationgofgthis .zeccentri'c. in a:-clc'ck.---

wi'senirectionacFigureii") 1withtthe; outwardiswin ingofweightedsarm 18acts to forcefthe pivotieye 1.61 :of' the=c1utch shoeomzan outwarddirection. forwcausing-engagement20f the clutch; Now let us:considerfawhatis taking iplace along: the are Y' :as the. axis. of theconnecting pin asxswmgs through a corresponding range of movement. Whenthe: weighted xleverais in its. inwardly-:retracted position, the-:axisofithis spring connecting pin. 85 has a; relatively-donglength. ofeffec* tive. radius-arm, or moment; arm iaround thecipivot of theweighted-lever; but asith'e :lever. v swings. outwardly iniresponse. toicentrifugaliiorce' the efl'ective zlengtheoffthis :radius :arrnvvcon'tinuously diminishes :untilv the; radius arm has-sia -much shorterlength when Lthev'spring connecting. pm isin the '45.degreeepositionsshown in figure It willahence be-se'enlthatathetensiomofthe:spring 82-:isr'transmitted itO the- WEiEht8d1EVe1T orto .'.the axis 0f the --actuating eccentric through sat en"-tinuouslydiminishing radius arm "as-the weighted lever: swings outwardlyin respons'eto increas ing engine speed. Preferably; the proportionsofthis diminishing-"ratio of eflective. lever iarm compared totheilength or *deflection change :of. the tension :spring :are suchthatiiathe aresistance offered the: pring: to continued outwardswinging. movementl of "weighted lever 'diminishes; even th u h the; tenf t Spring builds, up with increased elongation. Thus, it will be seenthat as soon as the centrifugal force acting along are X-isj largeenough to overcome the resistance force acting along the arc Y, theresulting outward-movementof the pivoted lever is quite rapid, becausethe resistance force continuously decreases at the same time that thecentrifugal force along arc X continuously increases. This results in; arelatively-quick engagement of the clutch after the prime mover hasreached the predetermined clutching speed. As previously described, theclutching engagement-is brought about by theturning movement of theactuating eccentric 15 which sets up a separating pressure between theeyes 13 and I4 of:.the pressure links and the eye 16 of the clutch shoe,whereby this end of the clutch shoe is forced outwardly into clutchingengagement againstthe inner surface of the driven drum 22. it will beseen from the foregoing that as the engine speed is increased for thepurpose of engaging the clutch, the centrifugally responsive weightedarm 8| assumes dominance over the opposing spring 82 at a substantiallypredetermined speed or range of speeds which I shall call theapproximate clutch engaging speed, at which point the clutch snaps intoengagement, because of the above described inverse relationship betweenthe increasing radius arm through which the Weighted lever acts and thedecreasing radius arm through which the op posing spring acts.

. Referrin now to the reverse operation of automatically releasing theclutch, when the engine speed is reduced to the point where thecentrifugal force acting on the weighted levers M is not suiiicient toovercome the tension pull of the springs 82, then the springs quicklyassume dominance over the weighted levers with the result that thelevers start to swing inwardly into a clutch releasing position. In thisinward swing ing movement the radius arm of the center of gravity C. G.-continuously diminishes in effective length, whereas the radius arm ofthe spring connectin pin' 85'continuously increases in effective length.Hence, it will be seen that when the clutch shoes start to release,theytrelease very quickly, thereby minimizing heating and wear of theclutch surfaces. "Figure 8 shows a typical set of performance curvesobtained in the operation of one of my improved clutches. The full-linerupwardly ex tending curves indicate the torque in inch-pounds exertedonthe actuating eccentric 15 by the weighted lever at different enginespeedsv and different angular positions of the weighted lever. Thedownwardly extending dotted line curve de notes the negative or opposingtorque in inchpounds which is exerted through connecting'pin 85upontheactuatin eccentric 15 by the resistance spring 82. This latter curve"slopes downwardly by reason of the continuously di-- minishing length ofeffective radius arm Y (Figure '7) as the weighted lever swingsoutwardly toward the clutch engaging position. The point Z at the lefthand end of the negative torque curve indicates the minimum break-awayspeed at which clutch engagement will be initiated, and the point Z' atthe 45 degree position on this negative torque curve indicates theapproximate speed at which clutch release will occur. It will be seenthat a speed oi. approximately 1200 R. P. M. or higher is necessary toovercome the negative torque of the spring and the static friction ofthe parts when'thewe ghted lever is inthe zero degree positiom.Similarly,-it will be seen from the point Z that the engine speed mustbe brought down to approximately 600 R. P. M. before the positive torque"exerted centrifugally by the weighted lever is equal Itodr less thanthe negative spring torque which will start disengagement. Thus, in thisexample, the ratio of clutch engaging speed to clutch releas ing speedis approximately in the relation of. 2 to 1. Other ratios can beobtained by proper proportioning of the parts. Similarly, the speedlevel of clutch engagement and of clutch release can be raised orlowered by increasing orde creasing the tension of the opposing springs82, as by adjustment of the eccentric anchoring studs 93. c 5 It will beseen from the foregoing description that therubber bushed; mounting I46, 41, 48 provides for the automatic centering of the clutch shoes 38:within the driven clutch drum 2 2 the event of angular'or offsetmisalignment of the driving and driven clutch elements. It also providesfor the reaction pressure of clutching engagement being transmitteddirectly from shoe to shoe with the only supporting connection betweenthe shoes and the driving ring 20 'a resilient connection through therubber bush;- ings 46, 41, 48. These rubber bushings also afaford a freefloating mountin for the pivoted centrifugal weights 8| and theretracting springs 82, whereby'these weights and springs become a partof the'floating assembly which includes the clutch shoes. Incidentally,any adjustments for wear effected by rotation of theadjusting eccentrics45 do not vary the tension of" the re?- tracting' springs 82 becausethe. spring support ing arms 52' and anchor studs 93 move bodily withthe rest of the assembly in such adjust:- ments. Operation of clutchesof this type has demonstrated the ability of the parts to perform theirintended functions even without the pres ence of the rubber 48. Forexample, in one in stance of a clutch operating under conditions ofextremely abnormal misalignment the rub her was actually burned out ofthe yielding "bush ings 4E, 41 and 48, but'the clutch "continued tofunction satisfactorily except that there was some objectionable noiseor clatter of the parts". While I" have illustrated and described what Iregard to he theprefer'red embodiment of my invention, nevertheless itwill be understood that such is'm'erely exemplary and that numerousmodifications and rearrangements may be made therein without departingfrom the essence of the invention. I claim: 5

l. Ina centrifugal clutch, the combination 01' a driving clutch element,a driven clutch drum; arcuate clutch shoes having anchored ends'pivotally carried by said driving element and hav ing swinging endsadapted to swing outwardly into clutching engagement with the interiorof said drum, resilient mounting means between said driving clutchelement and the anchored ends of said clutch shoes for permitting a limited degree of floating movement of' said anchored ends relativelyto'said driving clutch element adjusting eccentrics carried by saiddriving element for pivotally supporting the an"- chored ends of saidclutch shoes, links pivotally supported on said adjusting eccentrics,actuat ing eccentrics connecting said links with the swinging ends ofsaid clutch shoes whereby the clutch engaging pressure is transmittedfrom the swinging end of each shoe to the pivoted end :ofithe oppositeshoe by virtue of' the limited fi i ree of; floating movement of thepivotally anchored endpermitted bysaidresilientmounting means, adjustingmeans for rotating said adjusting eccentrics, centrifugally responsiveclutc'h engaging levers operatively connected with said actuatingeccentrics, and opposing springs connected to oppose clutch engagingmotion of saidlevers.

:2.- In a clutch, the combination of' a driving clutch element, .adriven clutch-drum, arcuate clutchshoesdriven by said driving elementand adapted to effect clutching engagement with said drum, adjustingeccentrics *pivotally mounting the pivoted ends-oi said clutch shoes onsaid driving clutch element, means operable :from the peripheryof theclutch 'for rotating said adjusting eccentrics to adjust the positions"of said shoes; actuating eccentrics mounted on separatecenters fromsaid adjusting eccentrics and operativel connected to-swing the swing-"ing ends of said shoes outwardly, and centrif- ,ugal' weights acting onsaid actuating eccentrics.

3; Ina clutch, the combination of .a. driving clutch element, a. drivenclutch drum, arcuate clutch shoes drivenby said drivingelement andadapted to effect clutching engagement with 'sa'id drurn, adjustingeccentrics pivotally mountfing-said clutchv shoes on said drivingclutchelement, worm. and gear means for rotating said "adjusting eccentrics toadjust. said shoes for weary links for connection with outwardlymovableends of'said shoes, actuating eccentrics connected with saidlinks, said actuating eccentries being-disposed on. "separate centersfrom saxi.d adjusting eccentrics, and; centrifugally .-re spons'ivemeans .forautomatically rotating said aotuatingeccentrics td engage saidclutch.

.4. in a clutch, the combination of ,a driving clutchp;element, 1adrivenclutch drum, arcuate clutch shoes driven by said,-.dr-iv'ingelement and adaptedto-eftect clutching engagement with said;drum, adjusting eccentrics piv.otally mount- .ing'psaid" clutch shoes onsaid, driving clutch element, links, pivotall-y-mounted on saidadjusting -:eccentrics;. actuating eccentrics pivotally con- :necting:the outwardly-swinging:ends of said links with the outwardly swingingends of' said clutch shoes pivotally swinging centrifugal weightsconnected with said actuating eccentrics and flpcragtive toturnsaidlatter eccentrics for automatically engaging, said clutch at asubstantially predetermined rangeof speeds, retracting'SIJIiHgSvCOI'I-DQCtQdfiat oneendnvith said centrif ugal weights,adjustable anchor means for adjustably attaching the other ends of saidsprings "itoesaidli-nks whereby the .tensionof said springs .mayfbevaried, and worm and 'worm wheelmeans 'operatively connected with saidadjusting eccentrics for-simultaneously adjusting said latter:eccentrics to take up wear of -the clutch shoes, said :anchor means forsaid retracting springs moving with the adjustments effected by saidadjusting eccentrics whereby .sa-idlatter adjustments do not varythe-tension of said springs.

"5. In an automatic centrifugal clutch, the combination of adriving'clutc'h ring, .a driven rclu-tch drum, centrifugally responsivearcuate clutch shoes adapted to swing outwardly intoclutchingengagementwith theinterior of said driven clutch drum, :each ofsaid-shoes having a pivotally anchored end and an outwardly swing- :ingend, mounting ipivot means carried by said driving clutch :ring,adjusting: eccentrics carried ibyrsaidmounting pivot means and on wliichthe anchoredends ofisaid clutch- ;shoes are pivoted; connecting linkshaving pivotally anchored ends and inwardly swinging ends, the pivotallyanchored ends of said links having pivotal mounting on said adjustingeccentrics, actuating eccentrics serving 'as-the pivotinginstrumentalities betweenthe-inwardly swinging ends of saidlinks andtheoutwardly swinging ends of the corresponding clutch shoes,centr-ifugally responsive weighted levers carried by said actuatingeccentricsfor actuating the latter in a clutch engaging direction atrelatively high speeds, retracting tension springs connected with saidweighted levers through lever arms which decrease in effective leng thas said weighted levers swing out- -wa-rdly in response'to higherspeeds, the parts "being 'soconstructed and proportioned that in suchoutward swinging movement of said 'weightedilevers-the rate at which theeffective length of said lever arm decreases is consider ably fasterthan the rate at which the tension in-said retracting spring increaseswith increased deflection, wherebyclutch engagement is caused to occurvery'suddenly at a relatively high speed closely approaching maximumspeed, and whereby clutch release is caused tooccur very suddenly ata'relativelylow speed considerably below that of-clutch engaging speed,and adjusting means accessible from the periphery of said clutchandhaving geared connection with said adjusting eccentrics for adjustingsaid clutch shoes.

6, ln anautomatic centrifugal clutch, the combination-of a drivingclutch ring, a driven clutch drum, centrifugally responsive arcuateclutch shoes adapted-to swing outwardly into clutching engagement withthe interior of said driven clutch drum, each of'said clutch shoeshaving a pivotally'anchored end and arr-outwardly swinging end, thedirection of rotation .of the clutch beingsuch thatthe outwardlyswinging end of each shoe: is the leading end of the shoe, pivoteyescarriedby said driving clutch ring, adjusting eccentrics mountedtherein, resilient bushingsinterposed between said pivot eyes and saidadjusting eccentrics to accommodate misalignment, said clutch shoeshaving their anchored ends-pivotally; mounted on said' adjusting eccentries, connecting links having pivotally anchored ends and inwardlyswinging ends, the pivotally anchored. ends of said links having pivotalmounting on said adjusting eccentrics, actuating eccentrics pivotallyinterposed between the inwardly swinging ends of'zsaid links and theoutwardly swinging ends of the corresponding clutch shoes,centrifugallyzresponsive Weighted levers carried by said actuatingeccentrics for actuatingthe latter'in-a clutch engaging direc tion inresponse to higher speeds, retracting springs connected :with saidweighted; levers each through-a-radius :arm which decreases in effectivelength as the weighted lever swings outwardly in responseto higherspeeds, the parts being so constructed and arranged that-insuch outwardswinging movement of the weighted lever the rateatwhich-theeffectivelength of said radius armxiallsioii is substantiallyfaster thanthe rate at which the tension in the spring :builds up withincreasing deflection, whereby clutch engagement is causedto occur verysudden-1y at a relatively high speed of said driving element, andwhereby clutch release is caused to occur very suddenly at a. relativelylow speed of; approxi- :mately acne-half that of clutch engaging S eed,and worm and gearvmeansifcr rotating said adjusting eccentrics to adjustsaid shoes for wear.

7. In an automatic centrifugal clutch, the combination of a drivingclutch ring, a driven clutch drum, arcuate clutch shoes adapted to swingoutwardly into clutching engagement with the interior of said drivenclutch drum, each of said clutch shoes having a pivotally anchored endand an outwardly swinging end, means pivotally mounting the anchored endof each clutch shoe on said driving clutch ring, connecting links 1having pivotally anchored ends and inwardly swinging ends, the pivotallyanchored ends of said links having pivotal mounting on said drivingclutch ring, actuating eccentrics disposed as the pivotinginstrumentalities between the inwardl swinging ends of said links andthe outwardiy swinging ends of the corresponding clutch shoes, saidactuating eccentrics functioning to exert a separating force between theshoes and the links tending to thrust the swinging ends of the shoesoutwardly and tending to exert an inwardly thrusting reactive force onsaid links, centrifugally responsive weighted levers connected with saidactuating eccentrics and adapted to rotate the latter for creating saidseparating force as said weighted levers swing outwardly in response tohigher speeds, opposing spring means connected to act on said weightedlevers in a clutch releasing direction, one end of each opposing springmeans being operatively connected with its associated weighted lever,and means for operatively connecting the other end of each opposingspring means with a reaction point on one of said connecting links.

8. In an automatic centrifugal clutch, the combination of a drivingclutch ring, a driven clutch drum, arcuate clutch shoes adapted to swingoutwardly into clutching engagement with the interior of said drivenclutch drum, each of said shoes having a pivotally anchored end and anoutwardly swinging end, mounting pivot means carried by said drivingclutch ring, adjusting eccentrics carried by said mounting pivot meansand on which the anchored ends of said clutch shoes are pivoted,connecting links having pivotally anchored ends and inwardly swingingends, the pivotally anchored ends of said links having pivotal mountingon said adjusting eccentrics at one side of the assembly, two-armmembers pivotall supported intermediate their ends on said actuatingeccentrics on the other side of the assembly and having one armextending substantially parallel with the associated connecting link,actuating eccentrics disposed as the pivoting instrumentalities betweenthe outwardly swinging ends of the clutch shoes and the inwardlyswinging ends of said connecting links and the adjacent arms of saidtwo-arm members, centrifugall responsive weighted levers carried by saidactuating eccentrics for actuating the latter in a clutch engagingdirection at a relatively high speed, retracting tension springs eachconnected with one of said weighted levers through a lever arm whichdecreases in eifective length as said weighted lever swings outwardly inresponse to higher speeds, and means for securing the other end of eachtension spring to the other arm of the associated two-arm member wherebysaid spring moves with said two arm member in pivoting or adjustingmovement of the latter.

9. In an automatic centrifugal clutch, the comating eccentrics servingas the pivoting bination of a driving clutch ring, a driven clutch drum,centrifugally responsive arcuate clutch shoes adapted to swing outwardlyinto clutching engagement with the interior of said driven clutch drum,mounting pivot means carried by said driving clutch ring, adjustingeccentrics carried by said mounting pivot means, each of said shoeshaving a pivotally anchored end and an outwardly swinging end, saidpivotally anchored ends being mounted on said adjusting eccentrics,connecting links having pivotally anchored ends and inwardly swingingends, the pivotally anchored ends of said links having pivotal mountingon said adjusting eccentrics, actu- 1nstrumentalities between theinwardly swinging ends of said links and the outwardly swinging ends ofthe corresponding clutch shoes, said actuating eccentrics functioning toexert a separating force tending to thrust the swinging end of the shoeoutwardl and tending to exert an inwardly thrusting reaction force onsaid links, centrifugally responsive weighted levers carried by saidactuating eccentrics, retracting tension springs connected with saidweighted levers through lever arms which decrease in effective length assaid weighted levers swing outwardly in response to higher speeds, theparts being so constructed and proportioned that in such outwardswinging movement of said weighted levers the rate at which theeffective length of said lever armdecreases is considerably faster thanthe rate at which the tension in said retracting spring increases withincreased deflection, whereby clutch engagement is caused to occur verysuddenly at a relatively high speed closely approaching maximum speed,and whereby clutch release is caused to occur very suddenly at arelatively low speed considerably below that of clutch engaging speed,an adjusting shaft carried by said driving clutch ring and extendingsubstantially diammetrically of the clutch across one side thereof,worms mounted on the end portions of said shaft, and worm wheels meshingwith said worms and mounted on said adjusting eccentrics wherebyrotation of said shaft is operative to angular-1y adjust said adjustingeccentrics through said worms and worm wheels.

CLARENCE M. EASON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 675,425 Sturtevant June 4, 19011,692,703 Rigolage Nov. 20, 1928 1,853,908 Lake Apr. 12, 1932 1,865,772Lyman July 5, 1932 1,869,097 Fawick July 26, 1932 1,917,501 CottermanJuly 11, 1933 1,939,601 Spalding Dec. 12, 1933 2,005,350 Rickwood June18, 1935 2,168,856 Banker Aug. 8, 1939 2,263,153 Wilson Nov. 8, 19412,375,909 Fawick May 15, 1945 2,392,950 Russell Jan. 15, 1946 2,419,784Low Apr. 29, 1947

